Antibiotic resistance is one of the most pressing global health challenges of our time, and Salmonella Typhi —the bacterium that causes typhoid fever—is no exception. For decades, Bangladesh has faced a high burden of typhoid fever, particularly among children. The rise in antimicrobial resistance (AMR) has made treating this disease increasingly difficult, especially with the widespread resistance to drugs like ciprofloxacin. In a groundbreaking 24-year study recently published in PLOS Neglected Tropical Diseases, researchers from the Child Health Research Foundation (CHRF) have provided critical insights into the trends of AMR in Bangladesh, showing both concerning and encouraging results.

Led by first author Arif Mohammad Tanmoy and supported by a collaborative team of national and international experts, the study tracks Salmonella Typhi isolates from 1999 to 2022, focusing on resistance to key antibiotics used to treat typhoid fever. The data were collected from two pediatric hospitals and three private clinics in Dhaka. The study includes an impressive 12,435 culture-confirmed cases, making it one of the most extensive surveillance efforts on AMR in typhoid fever to date.

One of the most significant findings of the study is the persistence of high resistance levels to ciprofloxacin, with over 90% of Salmonella Typhi isolates showing resistance. This trend is alarming, as ciprofloxacin has been a first-line treatment for typhoid since the 1980s. The consistent resistance suggests that the drug is no longer effective in the majority of cases in Bangladesh. On the other hand, resistance to older first-line drugs like cotrimoxazole, chloramphenicol, and amoxicillin has significantly declined, with multidrug resistance (MDR) dropping from 38% in 1999 to 17% in 2022. These findings indicate that these older antibiotics could be reintroduced as viable treatment options, particularly if resistance rates continue to fall below 5%.

The study also highlights the need for continuous monitoring and antibiotic stewardship. For instance, while resistance to ceftriaxone remains low (below 1%), the researchers observed a gradual increase in the minimum inhibitory concentration (MIC), signaling a slow but concerning trend that warrants close observation. Azithromycin resistance, first identified in 2013, remains under 4%, but its rising use may drive resistance in the future. The study establishes a crucial baseline for assessing the impact of future interventions, including the upcoming introduction of the typhoid conjugate vaccine (TCV) in Bangladesh, which is expected to significantly reduce the number of typhoid cases and, by extension, the use of antibiotics.

The importance of this study extends beyond Bangladesh. As typhoid remains a global health concern, particularly in low- and middle-income countries, the insights provided by this study can help guide global efforts to combat AMR. The findings are not only a call to action for improved antibiotic stewardship but also emphasize the importance of vaccination and preventive measures in reducing the burden of typhoid fever and limiting the spread of resistant strains.

This extensive research was made possible through the hard work of the CHRF team and the generous support of organizations like Gavi, the Vaccine Alliance, and the Bill & Melinda Gates Foundation. The study's senior authors, Dr. Senjuti Saha and Dr. Samir K. Saha, have long been advocates for improved diagnostics, surveillance, and vaccine implementation in Bangladesh, and this study is a testament to their dedication to combating infectious diseases and antimicrobial resistance.

As Bangladesh prepares for the introduction of the typhoid conjugate vaccine, the insights from this study will play a critical role in shaping public health strategies. The next few years will be crucial in monitoring the impact of these interventions, and continuous surveillance will ensure that Bangladesh remains at the forefront of the global fight against antimicrobial resistance.

Read full paper here - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0012558